With the rapid development of world economy, energy consumption is ever increasing, and countries in the world are in need of new energy to use widely. The greenhouse effect resulted from carbon dioxide emissions has caused global warming and natural disasters, making demand on clean and renewable energy by countries worldwide very strong. After the global crisis caused by the US subprime mortgage crisis in 2007 became more serious and widespread, each country has taken active measures to encourage the use of renewable energy, so as to stimulate economic growth. The Obama government bid to invest $150 billion into the development of clean energy in the next 10 years. The European Union has set a target that in 2020 renewable energy shall take up to 20% of the total used energy. Japan has proposed that more than 70 percent of newly-built houses would be installed with solar panels (about 70 GW) until 2030. To ease the shortage of domestic demands for photoelectric products, the Ministry of Finance of the People's Republic of China announced, on Mar. 26, 2009, the implementation of a model project “Solar Roofs Plan”. It is clearly stated in “Implementation Suggestions on accelerating applications of solar photovoltaics in buildings” jointly issued by the Ministry of Finance and the Ministry of Housing and Urban-Rural Development, that a series of principles and measures shall be taken to help implementation of the “Solar Roofs Plan”, including providing financial support to model projects which apply solar photovoltaics to buildings, promoting technical progresses and innovations, encouraging local governments to provide financial support, strengthening policy supports for the building field and so on. Currently, the application of solar energy technologies is well guided under the following strategies: for example, model projects involving solar roofs, photovoltaic curtain walls and other building integrated photovoltaics are actively promoted in economically advanced large and medium-sized cities having better infrastructures, off-grid power generating techniques are actively developed in rural and remote areas, and power is then transmitted to the countryside. By means of the solar roofs, photovoltaic curtain walls and other building integrated photovoltaics, people can better understand advantages of applying solar energy in a short time, which will also promote wider application thereof, and motivate industrial capitals to invest in the field of solar energy sources. Policies on new energy issued by individual countries will probably become one of the most important policies affecting the world development in the next 15 years. The Copenhagen Climate Conference in 2009 has woken up and strengthened people's awareness of clean energy sources once again. With the development and application of new energy, it is expected that the photovoltaic industry will experience further rapid growth.
An interconnect wire is an important material for soldering photovoltaic modules. The quality of the interconnect wire can therefore directly affect the efficiency of the photovoltaic modules for collecting current, which has a major impact on the power of the photovoltaic modules. It has always been a research topics of much interest in the interconnect wire area of how to increase the conversion rate and reduce the fragmentation ratio of solar cells by isomerizing the interconnect wire.
Chinese Patent application CN101789452A provides an interconnect wire coated with tin, which includes a copper wire with a tin layer coated thereon, where pits are uniformly distributed on a surface of the tin layer. With this interconnect wire, sunlight can be diffused in the pits to some extent, thereby increasing energy received from the sunlight. However, with just diffuse reflection occurs in the pits of this interconnect wire, only a small proportion of sunlight is reflected back to the solar cell, leading to a limited increase of the conversion rate. Furthermore, as the pits are fabricated when tin is coated on the copper wire, an uneven solder layer may be generated, which may cause the solar cells to be infirmly soldered with the interconnect wire, i.e., rosin joint might occur.
Chinese Patent application CN102569470A discloses a method of forming v-grooves perpendicular to a length direction of an interconnect wire on surfaces of the interconnect wire for reducing cracks and fragmentations of solar cells. However, in this type of interconnect wire, the v-grooves are perpendicular to the length direction thereof and there is no obvious gap between adjacent v-grooves. Therefore, this type of interconnect wire cannot be firmly soldered to solar cells, which may cause defective soldering joint.